1. Field of the Invention
The present invention relates to a small-sized keyboard apparatus which is suitable for mobile use.
2. Description of the Related Art
Conventionally, a keyboard apparatus is known which is small-sized for the convenience of mobile use. In general, a keyboard apparatus has a shape elongated in a direction in which keys are juxtaposed (in a lateral direction) (hereinafter referred to as “the direction of the row of keys) by its nature. Methods have been devised to reduce the size of the apparatus, including a method of configuring the apparatus as a folding type or a method of configuring the same as a roll-up type. For example, a folding type electronic keyboard apparatus is configured as disclosed in Japanese Laid-Open Utility Model Publication (Kokai) No. 61-76439 such that a keyboard section thereof is formed of a thin sheet, and the keyboard apparatus can be folded into a compact shape by folding the keyboard section at a dividing portion located between white keys without black keys interposed therebetween (between an E key and an F key, or between a G key and a C key) such that folded opposite portions of the top side of the keyboard or folded opposite portions of the back side of the same are faced and overlaid with each other.
However, when a folding member in general is folded, the inside (trough) of a bent portion (dividing portion) thereof is compressed and the outside (crest) of the same is expanded. This property or phenomenon is essentially possessed by a folding member unless the folding member has a thickness of zero which is actually impossible. Therefore, to actually manufacture the conventional keyboard apparatus, it is necessary to form a keyboard proper, which forms a sheet-shaped section, of a resilient material. This restrains the freedom of choice of materials. Further, even if the keyboard is formed of a resilient material, compared with an ordinary type (not a folding or roll-up type), it is low in rigidity and durability and limited in key stroke, which degrades the operability thereof. Further, since in the conventional keyboard apparatus, the keyboard is folded at the dividing portion by making use of the resiliency of the material of the sheet-shaped section, the dividing portion (folding portion) may develop a folded fatigue which can progressively affect the use's operation for performance, and the folding portion becomes lower in durability than the other portions. This impairs the balance of operability of keys. Further, the use of the resilient sheet makes it difficult to use a performance technique, such as glissando, and hence the operability of the keyboard apparatus is low from the start of use thereof. Thus, the conventional keyboard apparatus has problems in operability, rigidity, and durability.
Further, in the conventional keyboard apparatus, since folding thereof is performed between white keys without black keys interposed therebetween, the number of white keys arranged on one of keyboard units into which the keyboard is divided is three or four, and further, keys are necessarily arranged in such a pattern that the numbers of white keys in keyboard units are 3, 4, 3, 4, . . . , from the lowest tone range side. However, due to the difference in the number of white keys between the keyboard units, the keyboard units cannot be made uniform in length in the direction of the row of keys, so that the keyboard apparatus cannot be made sufficiently compact in size in the direction of the row of keys when it is folded, which leaves room in improvement in portability of the apparatus.
Incidentally, the aforementioned pattern of “. . . 3, 4, 3, 4, . . . ” in the number of white keys is also a requirement for molding an ordinary (not portable) keyboard apparatus. More specifically, in molding key units each having a plurality of keys integrally formed thereon, the key units are considered to be preferably divided between white keys without black keys interposed therebetween as described above so as to avoid the inconvenience that ribs of molds have excessively long thin portions which correspond to portions between keys. However, in designing a portable keyboard apparatus, thin ribs of the mold do not present a substantial problem since keys are formed to be thin and hence the ribs of the molds are low in height. What is more, since the key unit is thin, it can be manufactured by blanking a plate material or the like method, which makes it practically unnecessary to consider the above-described limitation to be imposed by molding. Consequently, it is considered unnecessary to stick to the above-mentioned pattern of “. . . , 3, 4, 3, 4, . . . ”.
Further, in reducing the size of the keyboard apparatus, it is desirable that the apparatus can be adapted to a wide range of musical scenes, in other words, to secure a minimum required number of keys or a minimum tone range necessary for a wide range of tunes, and prevent the use of the apparatus from being too limited. The minimum required number of keys considered to satisfy this requirement is preferably 20, 24, 25 or so in terms of the total of white and black keys. For example, in the case of 20 keys, a C key-to-F key arrangement in which the lowest tone corresponds to a C key and the highest tone corresponds to an F key can cover a required tone range necessary for a large number of tunes and has little inconvenience in performance. Similarly, in the case of 24 keys, it is preferred to employ an F key-to-E key arrangement in which that the lowest tone corresponds to an F key and the highest tone corresponds to an E key or a C key-to-B key arrangement in which the lowest tone corresponds to a C key and the highest tone corresponds to a B key. In the case of 25 keys, it is preferred to employ an F key-to-F key arrangement in which the lowest tone corresponds to an F key and the highest tone corresponds to an F key or a C key-to-C key arrangement in which the lowest tone corresponds to a C key and the highest tone corresponds to a C key. On the other hand, a key arrangement of 21 keys, 22 keys, or 23 keys has few advantages, and considered unpreferable from the viewpoint of effective use of limited space of the small-sized keyboard apparatus.
Further, also in arranging operating elements other than the keys, which are used for effects and the like, the layout thereof is required to be designed at the minimum cost of the portability and operability of the keyboard apparatus. Further, from the viewpoint of production, it is desirable to design the keyboard apparatus such that the number of kinds of components is reduced by using as many common or identical components as possible.
Further, due to the importance being laid on all of durability, portability, and operability, the keyboard apparatus is complicated in construction and difficult to manufacture.
Moreover, the portable keyboard apparatus tends to be narrower in tone range due to the minimized number of available keys. To compensate for this tendency, it is contemplated to provide a key range shift operating element for changing the pitch of a tone generated by depression of each key. In disposing this operating element, consideration is required so as to prevent the portability and operability of the apparatus from being degraded and the apparatus from becoming complicated in construction to no purpose.
Further, to generate tones according to depression of keys of the portable and small-sized keyboard apparatus, the keyboard apparatus is sometimes connected to another device or apparatus having an amplifier function. However, if it is desired to cause even the keyboard apparatus alone to generate simple tones, it is necessary to provide the keyboard apparatus with an acoustic transducer means, such as speakers. The acoustic transducer means is required to be disposed by designing such that the acoustic transducer means does not become a hindrance to reduction of the size of the keyboard apparatus so as to enhance the portability.